The projects to be described all concern on a molecular level the interaction between the human host and various bacterial pathogens. The pathogenic bacteria under study are to gonococcus, meningococcus, group A, and group B streptococcus. These studies have the ultimate aim of identifying antigens to serve as vaccine candidates for the prevention of these diseases of great importance. A second major aim of these projects is to attempt to understand how bacterial products derived from the group A streptococcus initiate glomerulonephritis and rheumatic fever. These studies are elucidating the human humoral and cellular immune response to relevant streptococcal antigens such as the cell wall, the cytoplasmic membrane, the heart cross-reactive factors, and a specific protein associated with strains causing glomerulonephritis. These studies have in common the need for the large-scale cultivation of moderately pathogenic organism and a 150 liter fermentor suitable for the cultivation of these organisms is required.